Digital-to-analog (DAC) converters have many applications, among them testing equipment and wave generators, which are sometimes also used in testing equipment. All the DACs in the device are synchronized using common phase detector hardware that measures the relationships between all the DAC outputs. The clocks are shifted until they are all aligned and the outputs of the DACs become de-skewed.
Issues arise in this method of synchronization because each DAC module need to have connections to the common phase detector circuit. This results in extra routing traces and less flexibility and re-use. If a system designer wanted extra channels, the phase detector would have to change to accommodate the extra DACs for the extra channels.